What would cause a localhost ModX site to revert to the remote URL?

I have a development ModX Revolution site running on a MAMP stack on my local machine. When I browse the site, I can browse the localhost version which tells me it's not a .htaccess or localhosts problem. But, when I go to the Admin backend, it always reverts to the production site on the Internet.

There must be something in one of the config files or in the server settings causing this. Problem is, I can't get to the server settings and the three config.core.php files are all at the default.

What am I missing? How can I get back into the admin screen?

Have you looked at the paths and URLs in the core/config/config.inc.php file?

Is there an .htaccess file in the Manager directory?

When you access the Manager, you're running the index.php file in the manager/ folder.
Also check for site_url setting in the System Settings and Context Settings.

Normally, MODX sets the site_url on the fly based on the URL the user comes in on. Without a setting somewhere, it shouldn't ever change from that.

There are a few plugins that modify the URL and could have a hard-coded URL, though that's fairly rare and they shouldn't contain a full URL.